Installation for the support of pivotal guide blades

ABSTRACT

An installation for the pivotal support of guide blades of turbo machines particularly gas turbines in which chambers or passages are provided in the bearing support through which flows the cooling air; the blade shaft constructed as adjusting shaft is provided with an annular groove in its center bearing area and with another annular groove at the blade end whereby the two annular grooves are connected with each other by a thread; the central annular groove is in communication with the chambers or passages while the other annular groove is in communication with the guide blade space of the machine.

United States Patent Loebel 1 Mar. 28, 1972 [54] INSTALLATION FOR THESUPPORT OF PIVOTAL GUIDE BLADES [72] Inventor: Woli Loebel, Munich,Germany AssigneeI Mqtorsmu urhinenrllnion Mun h GmbH, Germany [22]Filed: May 19,1970

[52] U.S.Cl ..415/110,415/116,415/147,

[51] Int. Cl ..F01d 1l/00, F04d 27/00 [58] Field ofSearch..415/109,110,111, 112,116, 415/115, 149, 150, 156; 416/95, 96, 97,156

[56] References Cited UNITED STATES PATENTS 3,525,574 8/1970 Zerlauth...

1,770,496 7/1930 Lawaczeck ..415/ 169 3,367,628 2/1968 Fitton ..415/110FOREIGN PATENTS OR APPLICATIONS 755,527 8/1956 Great Britain ..415/156Primary Examiner-l-lenry F. Raduazo Attorney-Craig, Antonelli and Hill 1ABSTRACT An installation for the pivotal support of guide blades ofturbo machines particularly gas turbines in which chambers or passagesare provided in the bearing support through which flows the cooling air;the blade shaft constructed as adjusting shaft is provided with anannular groove in its center bearing area and with another annulargroove at the blade end whereby the two annular grooves are connectedwith each .other by a thread; the central annular groove is incommunication with the chambers or passages while the other annulargroove'is in communication with the guide blade space of the machine.

18 Claims, 1 Drawing Figure INSTALLATION FOR THE SUPPORT OF PIVOTALGUIDE BLADES The present invention relates to an installation for thesupport of pivotal guide blades of turbo-machines, especially of gasturbines, whereby chambers or passages are provided in a bearingsupport, through which flows cooling air. Particular difficulties haveto be overcome in the support of pivotal guide blades of gas turbines,by reason of the large temperature range in which a satisfactoryoperation must be assured at all times, which difficulties consist inthat the bearing clearance necessary for the pivoting movement has to bemaintained notwithstanding the considerable thermal expansions.

It is known to cool the bearing places with compressed air in order toavoid large thermal expansions and the danger connected therewith of abinding of the guide blades. The heretofore known arrangements, however,provide only cooling passages or chambers in the bearing housing wherebythe cooling flow frequently cannot be conducted sufficiently close tothe hottest and therewith the most endangered places of the bearing sothat the desired cooling effect is completely absent or is attained onlyunsatisfactorily.

It is therefore the object of the present invention to provide a bearingsupport installation for guide blades, in which a cooling medium isconducted directly to the hottest places of the bearing and thus aneffective cooling of the bearing is achieved.

As solution to the underlying problems, it is proposed in accordancewith the present invention that a blade shaft constructed as adjustingor actuating shaft be provided with annular grooves in its centralbearing portion and at the blade end, which are connected with eachother by a thread with cylindrical external surfaces, whereby thecentral annular groove is in communication with the chambers or passagesconducting the cooling air and the annular groove at the blade side isin communication with the guide blade space of the machine.

The cooling air, which can be derived, for example, from a suitablecompressor stage or from a similar air supply, flows through the centralbore into the central annular groove of the blade shaft and from thereby way of the thread to the blade end of the shaft where it flows offinto the guide blade space by way of the second bore. The particularadvantage of this arrangement resides in that the bearing support iseffectively cooled at its hottest place; namely, at the blade shaftitself.

A further advantage resides in that the blade shaft and bearing bore arekept by the cooling system approximately at the same operatingtemperature at their contact places whereby the bearing clearance whichexists with a cold machine, remains approximately constant over theentire operating range (temperature range) of the machine.

Finally, an extradordinarily favorable sealing of the guide blade spacewith respect to the surrounding area is achieved simultaneously by thecooling air guide system of the present invention since the cooling airhas simultaneously the effect of a sealing medium.

In an appropriate construction of the present invention, the blade shaftincludes, starting from its central annular groove toward the outside, alabyrinth seal having cylindrical external surfaces and consisting of alarge number of annular grooves. The labyrinth is advantageously formedby a number of annular grooves of rectangular cross-section. With thistype of labyrinth, the cooling air flow from the shaft center in theoutward direction is kept as small as possible since it is only ofsubordinate significance for a cooling effect within this area and thecooling medium mass flow, which represents a loss, should be kept assmall as possible.

According to a further feature of the present invention, the blade shaftis constructed as hollow shaft which results in a relatively slight heatflow from the blade through the shaft so that the ratio of heattransferred to the bearing place to the heat removed by cooling can bekept small.

According to a further favorable construction of the bearing supportinstallation according to the present invention, a bearing bush withgood anti-friction properties is inserted between the bearing supportand the blade shaft, which bush is provided with inlet and outlet boresor ports for the cooling air corresponding to the bores in the bearingsupport.

The use of a bearing bush between housing and adjusting shaft offers theadvantage that a material can be selected for the bearing bush which,first of all, has good anti-friction properties that do not change orchange only slightly over a certain temperature range, without requiringat the same time high strength properties as are required, for example,in connection with the housing material. The good anti-frictionproperties must be ensured by a suitable material combination since areduction of the friction by, a lubricant must be consideredimpractical, Thus, by the use of anti-friction bushes, a favorable lowfriction clearance conditioned on the material can be attained at theblade adjusting shaft which results correspondingly in slight adjustingforces (moments).

According to a further feature of the present invention, the bearingbush is provided at its blade end with an offset of reduced diametricdimension so that an inwardly open annular space results between thehousing bore and bearing bush, through which the cooling air leaving thebearing bush is conducted into the main gas stream of the turbo-machine.Retuming the cooling air into the guide blade space through such anannular space offers the advantage that any combustion residues whichare deposited in the annular gap between the upper guide blade end andthe housing bore, are constantly blown off by the inwardly directed airstream and are returned to the main gas stream.

According to a further development of the present invention, the bladeshaft is provided at its blade end with an annular collar that abuts atthe inner end face of the housing or of the bearing bush. An outwardlydirected pressure force results at the annular collar from the gaspressure in the guide blade space which presses the annular collaragainst the end surface of the housing or bearing bush so that a goodseal of the guide blade space with respect to the bearing place isrealized.

In an advantageous manner according to a further feature of the presentinvention, a spring prestressed in the axial direction is provided whichis supported on the outer side of the bearing support, on the one hand,and on the blade shaft, on the other. This spring pulls the blade shaftoutwardly with its prestress so that it causes an abutment of theannular collar of the blade shaft at the inner end face of the bearingbush or housing also with a slight excess pressure in the guide bladespace and thus assures a good sealing effect.

These and further objects, features and advantages of the presentinvention will become more obvious from the following description whentaken in connection with the accompanying drawing which shows, forpurposes of illustration only, one embodiment in accordance with thepresent invention, and wherein;

The single FIGURE is a partial cross-sectional view through a guideblade adjusting mechanism of a gas turbine with a bearing bush inaccordance with the present invention.

Referring now to the single FIGURE of the drawing, a bearing bush 3 issecurely fitted into a bore 21 provided in a housing 2 forming a bearingsupport. A bore or port 5 is disposed approximately in the center of thebush 3 which is in communication by way of a further bore or port 25 inthe housing 2 with a cooling air passage 4 of the housing. At the innerend of the housing, the bush 3 is provided with a reduced diametricportion forming an offset 23 so that an annular space 22 remains betweenthe bore 21 and the bush 3 at this place. One or several radial bores 6of the bush 3 terminate in this annular space 22. The shaft of the guideblade 9 constructed as actuating or adjusting shaft 7 is supported inthe bush 3. The guide blade shaft 7 is provided at its blade end with anannular collar 8 and adjoining the same with an annular groove 18. Theshaft 7 is provided in the central area thereof, at the place of thebore 5 of the bush 3, with an annular groove 16. This annular groove 16is in communication with the annular groove 18 by way of several threadsof trapezoidal cross-section such as ACME thread form. The support ofthe shaft 7 takes place at the cylindrical outer surfaces of the thread17 within the bearing bush 3. Extending outwardly from the annulargroove 16, the shaft surface is provided with a number of annulargrooves 20 constructed as labyrinth seal. A pivot or actuating lever 13is clampingly secured to the outer end 12 of the blade shaft 7. Thepivoting of this adjusting lever 13 takes place by an adjusting oractuating ring 14 arranged at the housing 2. An axially prestressed diskor cup spring is provided between the lever 13 and the outer end face ofthe bush 3, on which rests a closure disk or carrying washer 10a; theprestress force of the spring 10 is transmitted by way of the lever 13to the blade shaft 7 so that the annular collar 8 of the shaft 7 ispressed against the end surface 30 of the bush 3, located at the innerside of the housing.

The compressed air supplied by an air source and flowing through one orseveral passages 15 into the space 4, flows through the bores and 5 intothe annular groove 16 between the bush 3 and the blade shaft 7.

From there, the cooling air flows inwardly and outwardly, following thepressure drop, and more particularly inwardly by way of the thread 17whereby it cools in an effective manner the blade shaft 7 and the bush3. After leaving the thread 17, the cooling air reaches the annulargroove 18 from where'it flows off by way of the bore 6 into the annularspace 22 and from there into the main stream duct 1. A very small amountof compressed air flows from the annular groove 16 in the outwarddirection by way of the labyrinth seal 20 and exits into the atmosphereat the spring 10 by way of gaps.

While I have shown and described only one embodiment in accordance withthe present invention, it is understood that the same is not limitedthereto but is susceptible of numerous changes and modifications asknown to those skilled in the art, and I therefore do not wish to belimited to the details shown and described herein but intend to coverall such changes and modifications as are encompassed by the scope ofthe ap pended claims.

I claim:

1. An installation for supporting pivotal guide blades of turbo-machinesin which at least one passage is provided in a bearing support throughwhich flows cooling air, characterized in that a blade shaft constructedas an adjusting shaft is provided with annular grooves in its centralbearing area and near the blade end thereof, which are in communicationwith each other by way of a thread, the central annular groove being incommunication with the passage conducting the cooling air while theannular groove near the blade end is in communication with the guideblade space of the machine.

2. An installation according to claim 1, characterized in that saidthread has substantially cylindrical external surfaces.

3. An installation according to claim 2, characterized in that the bladeshaft, starting from the central annular groove in the outwarddirection, is provided with a labyrinth seal means consisting of anumber of annular grooves.

4. An installation according to claim 3, characterized in that thelabyrinth seal means has cylindrical outer surfaces.

5. An installation according to claim 4, characterized in that the bladeshaft is constructed as a hollow shaft.

6. An installation according to claim 5, characterized in that a bearingbush means with good anti-friction properties is inserted between thebearing support and the blade shaft, said bush means being provided withinlet and discharge bores for the cooling air corresponding to thesupport means.

7. An installation according to claim 6, characterized in that thebearing bush means is provided near the blade end with a portion ofreduced diametric dimension so that an inwardly the blade shaft isprovided near the blade end thereof with an annular. collar that abutsat the inner end face of one of the two parts consisting of housing andbearing bush means.

9. An installation according to claim 8, characterized in that anaxially prestressed spring means is provided which is supported, on theone hand, on the'outer side of the bearing supportand, on the other, atthe blade shalt.

10. An installation according to claim 1, characterized in that abearing bush means with good anti-friction properties is insertedbetween the bearing support and the blade shah, said bush means beingprovided with inlet and discharge bores for the cooling aircorresponding to the support means.

11. An installation according to claim 10, characterized in that thebearing bush means is provided near the blade end with a portion ofreduced diametric dimension so that an inwardly open annular spaceresults between the housing bore and the bearing bush means, and in thatthe cooling air leaving the bearing bushmeans is conducted through theinwardly open annular space into the main flowchannel of the turbomachine.

12 An installation according to claim 1, characterized, in

that the blade shaft is provided near the blade end thereofwith.

an annular collar that abuts at the inner end face of one of the twoparts consisting of housing and bearing bush means. 1

, '13. An installation according to claim 12, characterized in that anaxially prestressed spring means is provided which is supported, on theone hand, on the outer side of'the bearing support and, on the other, atthe blade shaft.

14. An installation according to claim 12, characterized in that theblade shaft, starting from the central annular groove in the outwarddirection, is provided with a labyrinth seal means consisting of anumber of annular grooves.

15. An installation according to claim 1, characterized in that anaxially prestressed spring means is provided which is supported, on theone hand, on the outer side of the bearing support and, on the other, atthe blade shaft.

16. An installation according to claim 1, characterized in that theblade shaft, starting from the central annular groove in the outwarddirection, is provided with a labyrinth seal means consisting of anumber of annular grooves.

17. An installation for supporting pivotal guide blades ofturbo-machines, comprising a blade shaft formed as an adjusting shaftcarrying a blade at one end thereof, a bearing support surrounding saidshaft and having at least one passage for conducting cooling air, saidshaft being provided with an annular groove in its central bearing areaand an annular groove near the bladeend thereof, the central annulargroove being in communication with the passage conducting the coolingair while the annular groove near the blade end is in communication withthe guide blade space of the machine, the portion-of said blade shaftbetween the central and blade end grooves being provided with a helicalthread for communication therebetween.

18. An installation according to claim 17, wherein the portion of saidshaft extending from the central annular groove in the outward directionis provided with a labyrinth seal means in the form of a plurality ofannular grooves for preventing the flow of cooling air.

* i it

1. An installation for supporting pivotal guide blades of turbomachinesin which at least one passage is provided in a bearing support throughwhich Flows cooling air, characterized in that a blade shaft constructedas an adjusting shaft is provided with annular grooves in its centralbearing area and near the blade end thereof, which are in communicationwith each other by way of a thread, the central annular groove being incommunication with the passage conducting the cooling air while theannular groove near the blade end is in communication with the guideblade space of the machine.
 2. An installation according to claim 1,characterized in that said thread has substantially cylindrical externalsurfaces.
 3. An installation according to claim 2, characterized in thatthe blade shaft, starting from the central annular groove in the outwarddirection, is provided with a labyrinth seal means consisting of anumber of annular grooves.
 4. An installation according to claim 3,characterized in that the labyrinth seal means has cylindrical outersurfaces.
 5. An installation according to claim 4, characterized in thatthe blade shaft is constructed as a hollow shaft.
 6. An installationaccording to claim 5, characterized in that a bearing bush means withgood anti-friction properties is inserted between the bearing supportand the blade shaft, said bush means being provided with inlet anddischarge bores for the cooling air corresponding to the support means.7. An installation according to claim 6, characterized in that thebearing bush means is provided near the blade end with a portion ofreduced diametric dimension so that an inwardly open annular spaceresults between the housing bore and the bearing bush means, and in thatthe cooling air leaving the bearing bush means is conducted through theinwardly open annular space into the main flow channel of theturbo-machine.
 8. An installation according to claim 7, characterized inthat the blade shaft is provided near the blade end thereof with anannular collar that abuts at the inner end face of one of the two partsconsisting of housing and bearing bush means.
 9. An installationaccording to claim 8, characterized in that an axially prestressedspring means is provided which is supported, on the one hand, on theouter side of the bearing support and, on the other, at the blade shaft.10. An installation according to claim 1, characterized in that abearing bush means with good anti-friction properties is insertedbetween the bearing support and the blade shaft, said bush means beingprovided with inlet and discharge bores for the cooling aircorresponding to the support means.
 11. An installation according toclaim 10, characterized in that the bearing bush means is provided nearthe blade end with a portion of reduced diametric dimension so that aninwardly open annular space results between the housing bore and thebearing bush means, and in that the cooling air leaving the bearing bushmeans is conducted through the inwardly open annular space into the mainflow channel of the turbo-machine.
 12. An installation according toclaim 1, characterized in that the blade shaft is provided near theblade end thereof with an annular collar that abuts at the inner endface of one of the two parts consisting of housing and bearing bushmeans.
 13. An installation according to claim 12, characterized in thatan axially prestressed spring means is provided which is supported, onthe one hand, on the outer side of the bearing support and, on theother, at the blade shaft.
 14. An installation according to claim 12,characterized in that the blade shaft, starting from the central annulargroove in the outward direction, is provided with a labyrinth seal meansconsisting of a number of annular grooves.
 15. An installation accordingto claim 1, characterized in that an axially prestressed spring means isprovided which is supported, on the one hand, on the outer side of thebearing support and, on the other, at the blade shaft.
 16. Aninstallation according to claim 1, characterized in that the bladeshaft, starting from the central annular gRoove in the outwarddirection, is provided with a labyrinth seal means consisting of anumber of annular grooves.
 17. An installation for supporting pivotalguide blades of turbo-machines, comprising a blade shaft formed as anadjusting shaft carrying a blade at one end thereof, a bearing supportsurrounding said shaft and having at least one passage for conductingcooling air, said shaft being provided with an annular groove in itscentral bearing area and an annular groove near the blade end thereof,the central annular groove being in communication with the passageconducting the cooling air while the annular groove near the blade endis in communication with the guide blade space of the machine, theportion of said blade shaft between the central and blade end groovesbeing provided with a helical thread for communication therebetween. 18.An installation according to claim 17, wherein the portion of said shaftextending from the central annular groove in the outward direction isprovided with a labyrinth seal means in the form of a plurality ofannular grooves for preventing the flow of cooling air.